Measuring stream discharge using audible sound

Before we see a stream we can hear it. The discharge of that stream can be inferred from measurements of its sound. Sound pressure level is proportional to the energy of the flowing water and is related to discharge by a sound-discharge rating curve. Measurements with a hand-held sound level meter take seconds to acquire, allowing for high-resolution, long-term monitoring of stream discharge, campaign surveys, and ad hoc measurements. Sound measurements correlate well with the standard stream gauge data over the full range of discharges studied, from 0.02 m³/s to 33 m³/s. The following characteristics make the method an attractive alternative to the standard stream gauging: the instrumentation is simple and inexpensive; field deployment requires no built infrastructure; the instrument is suitable for rapid or emergency deployment; the measurements are non-invasive and non-contact, made at a distance from the stream, using a stationary or roving instrument; the acoustic response curve is linear; and the interfering sound sources are either negligibly small or easily removed.

If there is enough time, attendees will be able to create their own sound-discharge rating curve using their cell phones and the Decibel-X app to measure sound intensity. The conference room's audio equipment will provide sound clips of an actual stream along with the independently measured discharges.